Respiratory tract infections are a leading cause of morbidity and mortality worldwide. We identified a novel coronavirus from respiratory specimens obtained from children. This virus was simultaneously reported by two separate groups in The Netherlands. This virus, designated the New Haven coronavirus (HCoV-NH) is associated with upper and lower respiratory disease. Using RT-PCR, we identified this virus in 8.8% of respiratory samples from children who tested negative for common respiratory pathogens. The epidemiology of HCoV-NH is not yet defined. The first specific aim is to define the clinical epidemiology of HCoV-NH. To do this, 1) we will develop sensitive detection assays to detect HCoV-NH genome using RT-PCR. We will then develop an immunoassay to detect HCoV-NH antigen. This will be accomplished by developing HCoV-NH specific antibodies in experimental animals. We will also develop an ELISA to detect antibodies against HCoV-NH. ELISA will be based on HCoV-NH antigens, whole virus, recombinant HCoV-NH proteins, or synthetic peptides corresponding to the putative major antigenic proteins of HCoV-NH. 2) We will use the HCoV-NH specific ELISA to define the seroepidemiology of this virus in children. 3) We will also perform a population-based study to assess the impact and to define the clinical spectrum of respiratory disease associated with HCoV-NH. The second aim of this application will investigate the molecular epidemiology of this virus. To do this, 1) we will perform sequence and phylogenetic analysis on the spike gene of all isolates identified. We will determine whether there is substantial genetic variability of HCoV-NH in our community and between geographic locations. 2) We will study the evolution of this virus over time and identify specific areas of mutation. 3) We will determine whether genetic variants of HCoV-NH represent distinct serotypes and determine whether the clinical manifestations and disease severity are associated with specific genotypes.